FX = Foreign Exchange
HSBC charges a 3% foreign currency conversion fee for foreign ATM withdrawals, but no additional transaction fee for their own ATMs. You will pay a transaction fee for using non-HSBC ATMs. Also, if you use a different ATM from, say, a local bank, they will also likely charge a transaction fee.
One important thing to have if traveling abroad is a credit card that does not charge a foreign transaction fee.